1. Technical Field
The present disclosure relates to an organic light emitting diode (OLED) display device, and more particularly, to an OLED display device including a peak luminance controller and a method of driving the same.
2. Discussion of the Related Art
Among various flat panel displays (FPDs), organic light emitting diode (OLED) display devices have superior properties such as high luminance and low driving voltage. An OLED display device uses an emissive electroluminescent layer to realize high contrast ratio and thin profile, and is excellent at displaying moving images due to its short response time of several micro seconds (μsec). Also, an OLED display device has a wide viewing angle and is stable even at a low temperature. Since an OLED display device is typically driven at a low voltage of about 5V to about 15V in direct current (DC), a fabrication and design of a driving circuit is relatively easy. Further, a fabrication process for an OLED display device including a deposition and an encapsulation is simple.
Since an OLED display device is a current driving type where a current is supplied to a light emitting diode to emit a light, which is different from a liquid crystal display (LCD) device, it becomes more beneficial to reduce driving current and power consumption.
A peak luminance control driving method has been suggested as one of methods for reducing the power consumption of an OLED display device and will be illustrated hereinafter with reference to drawings.
FIG. 1 is a view illustrating a peak luminance controlling unit of an OLED display device according to the related art, and FIG. 2 is a graph showing a peak luminance change with respect to an average picture level and a gamma curve of an OLED display device according to the related art.
In FIG. 1, a peak luminance controlling unit 10 of an OLED display device according to the related art includes an average picture level calculating unit 20 and a peak luminance calculating unit 30.
The average picture level calculating unit 20 receives an image data RGB and calculates an average picture level APL of the image data RGB of one frame.
The peak luminance calculating unit 30 receives the average picture level APL from the average picture level calculating unit 20 and calculates a peak luminance PL using the average picture level APL for application to the image data RGB of one frame. The peak luminance calculating unit 30 may store an information on a correlation between the average peak level and the peak luminance PL.
In FIG. 2, the peak luminance calculating unit 30 calculates about 400 nit(=cd/m2) as the peak luminance PL at a first point ‘a’ where the average picture level APL is about 25%, calculates about 100 nit as the peak luminance PL at a second point ‘b’ where the average picture level APL is about 100%, and calculates a value between about 100 nit to about 400 nit as the peak luminance PL at a third point ‘c’ where the average picture level APL is between about 25% to about 100%.
The first point ‘a’ corresponds to a minimum average picture level where a peak luminance control begins, and the second point ‘b’ corresponds to a maximum average picture level having a minimum peak luminance. The first and second points ‘a’ and ‘b’ may variously change as desired.
As a result, when the average picture level APL is about 25%, the OLED display device displays an image of the corresponding frame according to a first gamma curve GCa where a luminance of a maximum gray level Gmax is about 400 nit. In addition, the OLED display device displays an image of the corresponding frame according to a second gamma curve GCb where a luminance of a maximum gray level Gmax is about 100 nit when the average picture level APL is about 100%, and the OLED display device displays an image of the corresponding frame according to a third gamma curve GCc where a luminance of a maximum gray level Gmax is between about 100 nit to about 400 nit when the average picture level APL is between 25% to about 100%.
The peak luminance PL calculated by the peak luminance controlling unit 10 is equal to or smaller than the maximum value of about 400 nit, and an image is displayed by using the peak luminance PL as a luminance corresponding to the maximum gray level of the image data RGB of one frame. As a result, a dynamic image can be displayed by using a relatively high luminance when the average picture level APL is relatively low, and the power consumption can be reduced by using a relatively low luminance when the average picture level APL is relatively high.
However, in the peak luminance control driving method according to the related art, since the peak luminance PL is controlled by analyzing merely the average picture level APL of the luminance information of an image, a perception level of the user may not be reflected. The perception level of the user may depend on color difference information of an image as well as luminance information of the image. Since the perception level of the user may not be reflected when controlling the peak luminance PL, the power consumption may be unnecessarily increased.